An adequate pigmentation is a major concern of the poultry industry. Not only it is synonymous of good healthy birds, but at the same time it is also an important marketing strategy in many cultures. Very frequently, poultry producers make considerable efforts in order to obtain an attractively pigmented bird-carcass that appeals to the eye of the consumer.
To satisfy the market preferences, chicken producers have traditionally supplemented the poultry diets with carotenoid (particularly hydroxicarotenoids or xanthophylls) containing extracts or meals of plant origin that are responsible for the desired yellow-orange color in the broiler chickens and in egg yolks. A widely used source of xanthophylls is marigold meal and its extract. The carotenoids from marigold contain approximately from 85 to 90% of lutein (.beta.,.epsilon.-caroten-3,3'-diol) and from 2 to 4% of zeaxanthin (.beta.,.beta.- caroten 3,3'-diol) (F. W. Quackenbush, 1972. J.AOAC, 55 (3), 617-21). These hydroxicarotenoids occur in the plant as esters of fatty acids, mainly palmitic, myristic and stearic (W. Gau. 1983, J. Chromatogr. 262, 277-84).
However, it has been proved that a more efficient pigmentation is obtained when the xanthophylls are in their free form (Fletcher, D. L. 1986, Poult. Sci., 65(9), 1708-14) after the ester link has been broken by means of a saponification process. As a matter of fact, most of the pigment producers carry on a saponification process in order to improve the bioavailability of the xanthophylls.
Furthermore, it has been demonstrated that a synergistic effect occurs when carotenoids like lutein and zeaxanthin are mixed with other natural or synthetic pigments for broiler chicken and egg yolk pigmentation (U.S. Pat. No. 3,539,686 of Nov. 10, 1970 to Ralph Rosenberg).
Different methods have been practiced in the past decades for the preparation of xanthophyll concentrates from marigold meal. As an example, in the U.S. Pat. No. 3,523,138 from Aug. 4, 1970. issued to Eastman Kodak Co., a process is described wherein the marigold meal is reacted with an alcoholic alkali solution. After saponification the mixture is diluted with water and the xanthophylls are separated by solvent extraction by means of water insoluble solvent like isopropyl ether.
U.S. Pat. No. 3,535,426 dated October 1970, issued also to Eastman Kodak Co., describes a method to stabilize xanthophylls by adding an antioxidant ethoxyquin (6.ethoxy-2,2,4-trimethil-1,2-hydroquinoline) and fat, and heating the mixture afterwards. The product obtained is very stable and does not degrade appreciably.
Also Ger. Offen. 2,535,963 dated Mar. 4, 1976, issued to CPC International Inc., describes a process to stabilize xanthophylls by partial saponification using a solution of potassium hydroxide in methanol.
U.S. Pat. No. 3,783,099 dated &gt;Jan. 1st 1974 issued to Ralston Purina Co., a process is described where an enzymatic hydrolysis of the cellulosic material of tho marigold meal, improves the extraction of the xanthophylls with a non polar solvent.
Recently some fermentative processes have been described wherein the reproduction of improved strains of Flavobacterium Multivorum result in the obtainment of zeaxanthin extracts with a pigment activity 2 to 3 times higher than that of marigold extracts, and are suggested as an alternative to naturally occurring carotenoids; as described on PCT Int. Appln. WO 91 03,571 dated Mar. 21, 1991, issued to Applied Biotechnology, Inc.
Traditional sources of zeaxanthin have been the extracts and meals of yellow corn and yellow corn gluten.
Years ago, Karrer and Jucker in 1947 (Helv. Chim. Acta. 30,266-7) obtained zeaxanthin by isomerizing lutein in a reaction catalyzed with sodium ethoxide in the presence of ethanol and benzene. A. G. Andrews, also in 1947 (Acta Chem. Scand. B 28 No. 1) obtained zeaxanthin from lutein using potassium methoxide in the presence of methanol and dimethylsulfoxide. In both procedures a poor yield was obtained resulting in a great loss of pigment. The economy of such processes is inadequate for industrial purposes. However, they demonstrated the feasibility to isomerize lutein into zeaxanthin.
In other words, isomerization of lutein into zeaxanthin has been carried out in academic research basis in a catalytic organic phase in the presence of solvents with a very strong alcoholic alkaline solutions which could cause a very violent exothermic reaction in the presence of water or humidity.
This process is related with the isomerization of lutein into zeaxanthin in a non catalytic aqueous phaso which does not needs the presence of solvents.
In the marigolds meal extracts available in the market, zeaxanthin represents only from 4 to 6% of the total xanthophill content. Since the pigment activity of this carotenoid is higher than that of lutein, applicants have developed a process where a higher. concentration of zeaxanthin is obtained, and hence the pigment efficiency of the extract containing this carotenoid is improved.